I have 2 4g III /30 cards with the 40D and no problems, Is the camera set to only use cards and NOT internal memory, maybe it's is seeing full memory on the internal side and not the card itself. Look at card pins make sure they are all there and not bent or missing. Make sure the internal memory is clear of pictures

tach18k wrote:
I have 2 4g III /30 cards with the 40D and no problems, Is the camera set to only use cards and NOT internal memory, maybe it's is seeing full memory on the internal side and not the card itself. Look at card pins make sure they are all there and not bent or missing. Make sure the internal memory is clear of pictures

What internal memory?

The problem is real and occurs under certain PRECISE circumstances WITH CERTAIN VERSIONS OF THE 4gb CARD.

If you haven't experienced the issue, you are fortunate, it doesn't mean it doesn't exist.

Yes the 40D is very strange, similar to the 85L battery metering issues, it seems certain models are affected, but not others.

The only thing I can think of as an explanation is if Canon changed a component or material or something between production runs, which causes issues like this or the 85L II issue in certain 40Ds but not others